3. PLACEBO: Placebo for MNA administered as an identically appearing oral dose Each treatment period will consist of a 3-day two-night confinement cycle with admission on day 1, treatment on day 1 with a single dose of active or placebo with discharge 24 hours following the last assessment the next morning. A washout period of 5 days will separate each treatment period. Standard biochemical and clinical baseline medical background and physical examination will occur at screening and at Day -1 to assess/confirm entry criteria. During each treatment period, serial plasma samples (n=12) for MNA assay will be collected on the treatment day. Safety assessments, including vitals signs (blood pressure, pulse rate, respiration rate, and oral body temperature), will be performed at screening, at baseline, and at 4 times throughout each treatment period. Physical examinations and standard clinical laboratory tests (hematology, serum chemistry, and urinalysis) will be obtained at screening, and at admission for each treatment period, and prior to subject's final discharge from the study. The Lunch meals on the dosing day will be identical in each subject on each occasion.